The present invention relates to a method of making a sheet metal part for motor vehicles.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
Heretofore, sheet metal parts for motor vehicles, also of relatively uniform profile and slight curves, with or without blank holders, are produced on a large scale using drawing or press forming processes. This is applicable for cold forming as well as press hardening of the sheet metal parts which are hot formed in a cooled die at initial temperatures of above 900° C. and then allowed to cool down in the die to harden.
As the advance of the blank into the press tool varies in dependence on many factors, the position of edges to be cut fluctuates greatly so that most parts require subsequent edge trimming. Also the position and shape of holes introduced into the blank beforehand fluctuates widely so that oftentimes there is a need for re-perforation.
Subsequent trimming and perforating is unwanted in particular when hot formed and press hardened parts are involved. In addition to the need for a separate working step which is not easy to integrate in the manufacturing process for hot formed hardened parts, mechanical trimming of hardened metal sheets exposes tools and machineries to substantial strain which causes significant wear. Moreover, trimming requires also additional material supply. Also, the thickness of the metal sheet and the outline of the edge being cut limits the application of technical and economical options for mechanical cutting, or requires cutting by thermal means, e.g. laser cutting. Finally, the strength of edges that have been cut mechanically and also thermally is impaired and is prone to fissure as a result of microcracks, notches and hardening.
It would therefore be desirable and advantageous to provide an improved method of making a metal sheet for motor vehicles to obviate prior art shortcomings.